After over two decades of attempts to agree on measures to stabilize the global greenhouse gas concentrations below a level deemed dangerous, the Paris Agreement will be the first legally binding agreement by which the Parties to the UNFCCC consent to urgently needed climate mitigation and adaptation actions to keep the average temperature rise below 2°C.

In enhancing the implementation of the UNFCCC, the Paris Agreement aims to strengthen the global response to the threat of climate change by (see Article 2.1):

(a) Holding the global average increase in temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the increase to 1.5°C above pre-industrial levels;

(b) Increasing the ability to adapt to the adverse impacts of climate change and foster climate resilience as well as low greenhouse gas emissions development; and

In the decision adopting the Paris Agreement, the Conference of the Parties to the UNFCCC recognise that:

climate change represents an urgent and potentially irreversible threat to human societies and the planet and thus requires the widest possible cooperation by all countries, and their participation in an effective and appropriate international response, with a view to accelerating the reduction of global greenhouse gas emissions (preambular consideration).

Notwithstanding this recognition, the Agreement is rather light on obligations to cooperate. Article 6 merely recognises that "some Parties" may "choose to pursue voluntary cooperation in the implementation of their nationally determined contributions" (Article 6.1), and uses the language of "engaging on a voluntary basis in cooperative approaches" (Article 6.2).

Similarly, Article 7 provides that Parties "recognize the importance of support for and international cooperation on adaptation efforts" (Article 7.6) but only provides that "Parties should strengthen their cooperation on enhancing action on adaptation" (Article 7.7).

Another cooperation "should" can be found in Article 11, which includes the stipulation that all Parties "should cooperate to enhance the capacity of developing country Parties to implement this Agreement" (Article 11.3)

On the other hand, the Agreement does provide that Parties "shall strengthen cooperative action on technology development and transfer" (Article 10.2), and that Parties "shall cooperate in taking measures, as appropriate, to enhance climate change education, training, public awareness, public participation and public access to information" (Article 12).

It should be noted that the term "Parties" to the Agreement refers not only to State Parties but may also include regional economic integration organizations and their member States (see Article 20.2, and for instance Articles 4.16 and 4.18). As a consequence, the cooperation obligations could also come to apply to regional organisations such as the EU or MERCOSUR.

Moreover, the Paris Agreement establishes cooperation obligations between specific bodies. Article 8.2 subjects the Warsaw International Mechanism for Loss and Damage associated with Climate Change Impacts to the authority and guidance of the Conference of the Parties to the UNFCCC (serving as the meeting of the Parties to the Paris Agreement). This Warsaw International Mechanism "shall collaborate with existing bodies and expert groups under the Agreement, as well as relevant organizations and expert bodies outside the Agreement." (Article 8.5).

The Agreement also establishes a "mechanism to facilitate the implementation of and promote compliance with the provisions of this Agreement" (Article 15.1). This mechanism shall consist of a committee "that shall be expert-based and facilitative in nature and function in a manner that is transparent, non-adversarial and non-punitive" (Article 15.2). However, it is at present unclear how and to what extent the Parties to the Paris Agreement will have to cooperate with this mechanism. The modalities and procedures under which the committee shall operate are yet to be established by the meeting of the Parties to the Paris Agreement.

As to potential disputes involving cooperation obligations on climate change action, it should be noted that Article 24 renders the UNFCCC dispute settlement provisions applicable. This is important because the UNFCCC envisages specific modalities for the settlement of disputes between two or more Parties. This includes settlement of the dispute through "negotiation or other peaceful means of their own choice" (Article 14.1), or - if the Parties fail to do so - by a conciliation commission that will "render a recommendatory award, which the Parties shall consider in good faith" (Article 14.6), or - if the Parties deposit a declaration recognising by reciprocity "as compulsory ipso facto and without special agreement" (Article 14.2) the submission of the dispute to the International Court of Justice or to arbitration.

Disputes on climate change action have yet to appear before the International Court of Justice but do feature in particular in the work of the Permanent Court of Arbitration (PCA). The PCA has adopted Optional Rules for Arbitration of Disputes Relating to the Environment and/or Natural Resources (2001), inter alia, to serve as procedural rules for the settlement of disputes between Parties to multilateral environmental agreements (including the UNFCCC and related agreements). At the COP21 in Paris, the Secretary-General of the Permanent Court of Arbitration was able to reveal that six of the disputes administered by the PCA concerning carbon trading, the Clean Development Mechanism, and Joint Implementation, have been brought under these Rules. It seems likely that the Paris Agreement will further add to the work of the PCA in this field.

The Paris Agreement will enter into force after at least 55 Parties to the UNFCCC accounting for at least 55 percent of the total global greenhouse gas emissions ratify the Agreement (Article 21.1).